In the following the expression “multifunctional device” is used to refer to an RFID device that is capable of operating as an RFID reader, is further capable of emulating an RFID tag, and can further be used for exchanging data with another RFID “multifunctional device” similar to the data transmission between an RFID tag and an RFID reader.
The data exchange between different multifunctional devices entails that it is not possible to determine the actually used functionality of a device. In the following the expression “initiator” will be used to refer to a device sending a signal for initiating near field communication. In the conventional RFID architecture the initiator is always the RFID reader requesting data. In the case of multifunctional devices the initiator can request to receive data or can request to dispatch a data transmission.
In the following the expression “target” will be used to refer to a device an initiator sends an initiation signal to. Actually there can be two different kinds of targets: active and passive targets. In the conventional RFID-reader/tag architecture there are only passive targets, i.e. RFID tags always providing the initial data transmission.
In the multifunctional device architecture the multifunctional device can be in the role of an active target or can be in the role of a passive target. In case the passive target role is adopted, the multifunctional device emulates a conventional RFID tag. In case the active target role is adopted, the multifunctional device can actively exchange data by using its own local power. The data exchange is not limited by a tag size when communication is performed between multifunctional devices, or multifunctional devices and other NFC devices or infrastructures. In the active target role, the multifunctional device can also request information or data.
Presently RF-tagging technologies, such as for example the RFID technology employ inductive or capacitive coupling in the radio frequency (RF) portion of the electromagnetic spectrum. RFID readers include at least an antenna, a receiver and a transmitter, where an RF signal may be transmitted and received by the RFID reader. An RF signal activates transponders or “tags” when brought in contact with or when brought within a predetermined local range of the tags. When a tag has been activated it transmits information back to the RFID reader. More particularly, in the case of a passive tag (i.e. having no local power source), the tag may be energized by a time-varying electromagnetic RF wave generated by the RFID reader. When the RF field passes through the antenna coil associated with the tag, a voltage is generated across the coil. This voltage is ultimately used to power the tag, and makes it possible that the tags return transmissions of information to the reader, sometimes referred to as “coupling”.
Actually there are different near field communication standards available on the market, such as e.g. ISO14443-4, Mifare, FeliCa, NFC and ECMA352.
A document related to the technological background of RFID tags is US 2004-0077383-A1, disclosing the technology of an enhanced RFID tag.
In case of the standard application of RFID technology a proprietary RFID reader is located in an environment with only a single type of RFID tag. With standard applications it is not necessary for a device to deal with different kinds of RFID tags in a single environment. For example in a stockroom or a supermarket there is no reason to use different types of RFID tags of different manufacturers that can consequently only be read by different readers. The use of different tags increases the expense of providing different kinds of readers and additionally may cause compatibility problems.
Several polling schemes have been used in the past, but none is fully suitable for use with RFID interactions between mobile devices.
The RFID technology can now be extended to an NFC (near field communication) implementation in mobile multifunctional devices enabling them to have interactions with tags, readers and with each other. The interaction between each other results from the ability to read out RFID tags i.e. the ability to send RF signals and the possibility to process returned RF-signals. The expense necessary to implement the ability to emulate an RFID tag into an RFID reader is very small, as signal processing capabilities, a transmitter and a receiver are already provided. In a conventional initiation process “cardwarming signals” are usually employed to wake up transponder devices or to power up RFID tags that are not provided with a built-in power supply. This capability can be used to transfer different data from one mobile tag-reader (emulating a tag) to a standard reader.
Interest in and use of various RF-tagging technologies has recently grown significantly, resulting in the development of various RF-tagging applications outside the conventional manufacturing line and electronic article surveillance applications. RF-tagging technologies are predicted to become one of the leading technologies providing short-range interaction applications in the near future, especially in a mobile communication environment.
All the conventional approaches for detecting RFID tags above have in common that they are not suitable for use with mobile multifunctional devices such as mobile phones or handheld computers. This is caused by the fact that on the one hand RFID tags are still proprietary applications using only a single kind of RFID tags, and on the other hand by the fact that the possibilities of RFID technology for data exchange between mobile devices have not yet been fully recognized.